Purification process for the preparation of non-carrier added copper-64

ABSTRACT

Compositions comprising high levels of high specific activity copper-64, and process for preparing said compositions. The compositions comprise from about 2 Ci to about 15 Ci of copper-64 and have specific activities up to about 3800 mCi copper-64 per microgram of copper. The processes for preparing said compositions comprise bombarding a nickel-64 target with a low energy, high current proton beam, and purifying the copper-64 from other metals by a process comprising ion exchange chromatography or a process comprising a combination of extraction chromatography and ion exchange chromatography.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Application No. 17/993,186, filed Nov. 23, 2022, which is a continuation of U.S. Application No. 17/894,874, now issued as U.S. 11,581,103, filed Aug. 24, 2022, which is a continuation of U.S. Application No. 17/446,443, now issued as U.S. 11,521,762, filed Sep. 3, 2021, which claims the priority of U.S. Provisional Application Serial No. 63/074,356, filed Sep. 3, 2020, the disclosures of which are hereby incorporated by reference in their entirety.

FIELD

The present disclosure relates to compositions comprising high levels of high specific activity copper-64, and process for preparing said compositions.

BACKGROUND

Diagnostic nuclear medicine uses two imaging techniques - single photon emission tomography (SPECT) and positron emission tomography (PET), often in conjunction with computerized tomography (CT) or magnetic resonance imaging (MRI). Of the two imaging techniques, PET provides higher resolution images and quantitative information. The enhanced capabilities of PET have generated higher demand for radiopharmaceutical agents that are capable of being imaged using this technique, thus necessitating the production of commercial quantities of radioactive precursors capable of PET for routine clinical use.

Common clinically-used PET isotopes include oxygen-15 (¹⁵O), nitrogen-13 (¹³N), carbon-11 (¹¹C), fluorine-18 (¹⁸F), and gallium-68 (⁶⁸Ga). Each of these isotopes, however, has a relatively short half-life, which necessitates producing them in close proximity to the PET imaging device and incorporating them into imaging agents before excessive radioactive decay or drug product decomposition occurs. A generator system for ⁶⁸Ga is available but it can be difficult to obtain and severely limits the number of doses that can be prepared in a day. To address the limitations of the short half-life radionuclides, PET isotopes with relatively longer half-lives have been investigated for development of new diagnostic PET agents.

Copper-64 (⁶⁴Cu) is a ‘non-standard isotope’ that can be used in diagnostic nuclear medicine. It is a radionuclide with excellent characteristics for PET imaging. Its average positron energy of 278.2 keV provides high resolution images, and its moderate half-life (12.7 h) is suitably long to allow for production, purification, incorporation into a carrier molecule (e.g., peptide, small-molecule, antibody, etc.) and distribution to medical facilities as an end-use product.

For widespread availability of ⁶⁴Cu on a commercial scale, large quantities of ⁶⁴Cu (i.e., Ci or GBq amounts) must be produced and isolated in a highly pure and chemically useful form (e.g., ⁶⁴Cu copper chloride) for use as a radioactive precursor. Preparations of ⁶⁴Cu copper chloride have been produced from isotopically enriched nickel-64 (⁶⁴Ni) targets, and the ⁶⁴Cu has been purified using ion exchange chromatography. In references located as of 2020, the highest reported amount of ⁶⁴Cu produced was 1.5 Ci, reported at end of bombardment (EOB). While this amount is sufficient for preparing patient doses, when factoring in decay and yield loss during manufacturing (i.e., formulation, sterilization, dispense, quality control, packaging and shipment) - 1.5 Ci of ⁶⁴Cu at EOB may yield 50 patient doses in a best-case scenario (assuming an average patient dose of 4 mCi, 32 h for manufacturing and shipment and 15% yield loss). The number of theoretical patient doses may be significantly improved by increasing the available quantity of ⁶⁴Cu copper chloride precursor. The ⁶⁴Cu must be of high chemical and radionuclidic purity.

Specific activity (i.e., activity of ⁶⁴Cu per mass of total Cu) of ⁶⁴Cu copper chloride is an indicator of its chemical purity and is often expressed in units of mCi/µg or Ci/mmol. In references located as of 2020, the highest reported specific activity of purified ⁶⁴Cu copper chloride was 348 mCi/µg Cu. This is sufficient for radiolabeling, but improvements in specific activity may improve the purity and reactivity of a radioactive precursor, thereby decreasing the required amount of carrier molecule necessary in production of a radiolabeled pharmaceutical. This has implications for patient safety and may enhance the diagnostic capability of a radiopharmaceutical. Improvements in specific activity of ⁶⁴Cu may be made by increasing the produced quantity of radioactive precursor, limiting the potential for introduction of trace metallic contaminants and creating a robust purification process.

If ⁶⁴Cu were widely available, it would enhance the capabilities of existing PET centers and would also allow PET studies to be performed at medical centers that do not have an on-site ⁶⁸Ge/⁶⁸Ga generator and/or do not rely on a regional cyclotron. Described herein are methods of making purified ⁶⁴Cu having improved chemical and radionuclidic purities and a specific activity that is favorable for supplying commercial clinical needs of PET and medical centers.

SUMMARY

Among the various aspect of the present disclosure are compositions comprising high levels of ⁶⁴Cu with high purity and high specific activity and processes for preparing said compositions.

One aspect of the present disclosure provides a composition comprising from about 2 Ci to about 15 Ci of ⁶⁴Cu at end of bombardment (EOB). The composition is obtained from a single target during one cyclotron run. The composition has a specific activity up to about 3800 mCi ⁶⁴Cu/µg Cu. In some embodiments, the composition comprises a solution of hydrochloric acid, such that the ⁶⁴Cu exists as [⁶⁴Cu]CuCl₂.

A further aspect of the present disclosure encompasses a process for preparing the ⁶⁴Cu from ⁶⁴Ni. The process comprises (a) bombarding a cyclotron target comprising ⁶⁴Ni with a proton beam to generate a bombarded target; (b) stripping the bombarded target with a volume of HCl having a molarity of about 6 M to about 12.1 M to form a strip solution comprising ⁶⁴Ni and ⁶⁴Cu; and (c) purifying the ⁶⁴Cu from the strip solution by ion exchange chromatography, wherein the ion exchange chromatography comprises (i) passing the strip solution through a column comprising an ion exchange resin such that ⁶⁴Cu binds to the ion exchange resin and ⁶⁴Ni passes through the column as a flow-through; (ii) rinsing the column with a volume of HCl having a molarity of about 3 M to about 6 M; and (iii) adding a volume of HCl having a molarity of about 0.5 M to about 3 M to the column to elute the ⁶⁴Cu from the ion exchange resin and collecting an eluate comprising ⁶⁴Cu.

Another aspect of the present disclosure encompasses an additional process for preparing ⁶⁴Cu from ⁶⁴Ni, wherein the ⁶⁴Cu is purified by a combination of extraction chromatography and ion exchange chromatography. The process comprises (a) bombarding a cyclotron target comprising ⁶⁴Ni with a proton beam to generate a bombarded target; (b) stripping the bombarded target with a volume of HCl having a molarity of about 6 M to about 12.1 M to form a strip solution comprising ⁶⁴Ni, ⁶⁴Cu, ⁶¹Co, and other or more other metals; and (c) purifying the ⁶⁴Cu from the strip solution by chromatography, wherein the chromatography comprises (i) passing the strip solution through a first column comprising an extraction resin connected in series to a second column comprising an ion exchange resin, such that the one or more other metals binds to the extraction resin in the first column, ⁶⁴Cu and ⁶¹Co bind to the ion exchange resin in the second column, and ⁶⁴Ni passes through both columns as a first flow-through fraction. The process further comprises (ii) rinsing the first and second columns with a volume of HCl having a molarity of about 6 M to about 12.1 M to remover residual ⁶⁴Ni as a second flow-through fraction; (iii) rinsing the second column with a volume of HCl having a molarity of about 3 M to about 6 M to elute ⁶¹Co as a first waste fraction; (iv) rinsing the second column with a volume of NaCl having a molarity of about 3 M to 6 M in HCl having a molarity of about 0.01 M to about 3 M or with a volume of HCl having a molarity of about 3 M to about 6 M to elute residual ⁶¹Co as a second waste fraction; and (v) adding a volume of HCl having a molarity of about 0.01 M to about 3 M to the second column to elute the ⁶⁴Cu as a product fraction comprising ⁶⁴Cu.

Other aspects and iterations of the present disclosure are detailed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a schematic of the purification process comprising ion exchange chromatography.

FIGS. 2A, 2B, and 2C present various embodiments of the purification process comprising a combination of extraction chromatography and ion exchange chromatography,

FIG. 3 is a plot of proton energy as a function of proton beam radius.

DETAILED DESCRIPTION

Provided herein are compositions comprising high levels of high specific activity ⁶⁴Cu and processes for preparing said compositions. The processes disclosed herein are able to produce high levels of ⁶⁴Cu from a single target during one continuous cyclotron bombardment (i.e., cyclotron run). The ⁶⁴Cu produced by these processes has a high specific activity, as well as high chemical and radionuclidic purities. Favorably, the ⁶⁴Cu compositions produced by the processes disclosed herein also have low levels of metal impurities such as cobalt, iron, nickel and lead.

(I) Compositions

The ⁶⁴Cu compositions disclosed herein comprise high levels of high specific activity ⁶⁴Cu. In general, the ⁶⁴Cu compositions comprise up to about 15 Ci of ⁶⁴Cu and have specific activities up to about 3800 mCi ⁶⁴Cu/µg Cu. The ⁶⁴Cu compositions may be prepared by the processes described below in sections (II) and (III).

The ⁶⁴Cu activity (Ci or Bq) may be measured by gamma spectroscopy (e.g., high purity germanium (HPGe) detector), a dose calibrator, or similar means. Specific activity (mCi ⁶⁴Cu/µg Cu) may be determined by measuring the mass of Cu by a variety of methods including inductively coupled plasma optical emission spectroscopy (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), or titration.

In general, the compositions disclosed herein comprise from about 2 Ci to about 15 Ci of ⁶⁴Cu at the end of bombardment (EOB). The level of ⁶⁴Cu may be determined at EOB or a later time point. Persons skilled in the art understand that the level of ⁶⁴Cu activity decreases over time. In some embodiments, the compositions may comprise from about 2 Ci to about 3 Ci, from about 3 Ci to about 4 Ci, from about 4 Ci to about 5 Ci, from about 5 Ci to about 6 Ci, from about 6 Ci to about 7 Ci, from about 7 Ci to about 8 Ci, from about 8 Ci to about 9 Ci, from about 9 Ci to about 10 Ci, from about 10 Ci to about 11 Ci, from about 11 Ci to about 12 Ci, from about 12 to about 13 Ci, from about 13 to about 14, or from about 14 to about 15 Ci of ⁶⁴Cu. In other embodiments, the composition may comprise from about 4.0-4.5 Ci, from about 4.5-5.0 Ci, from about 5.0-5.5 Ci, from about 5.5-6.0 Ci, from about 6.0-6.5 Ci, from about 6.5-7.0 Ci, from about 7.0-7.5 Ci, from about 7.5-8.0 Ci, from about 8.0-8.5 Ci, from about 8.5-9.0 Ci, from about 9.0-12.0, from about 12.0-15.0, from about 4.0-5.5 Ci, from about 5.5-7.0 Ci, from about 6.0-7.5 Ci, from about 7.0-8.5 Ci, r from about 7.5-9.0 Ci, or from about 9.0-15.0 Ci of ⁶⁴Cu.

In other embodiments, the compositions may comprise from about 2 Ci to about 5 Ci of ⁶⁴Cu at EOB, from about 5 Ci to about 9 Ci of ⁶⁴Cu at EOB, or from about 9 Ci to about 15 Ci at EOB. In further embodiments, the compositions may comprise from about 2 Ci to about 5 Ci of ⁶⁴Cu (at EOB) after about 2-4 h of bombardment, or about 5 Ci to about 9 Ci of ⁶⁴Cu (at EOB) after about 6 h of bombardment, or about 4 Ci to about 15 Ci of ⁶⁴Cu (at EOB) after about 8-12 h of bombardment.

Each of the compositions disclosed herein may be produced during a single cyclotron run and/or may be obtained from a single cyclotron bombardment.

The radionuclidic purity of the ⁶⁴Cu compositions disclosed herein is generally greater than about 98.5%, greater than about 99%, greater than about 99.5%, or greater than about 99.9% (referenced at 6 am of the day after bombardment).

The specific activity of the ⁶⁴Cu in the compositions disclosed herein may be as high as about 3800 mCi ⁶⁴Cu/µg Cu at EOB. Those skilled in the art understand that the specific activities of the compositions decrease over time. In various embodiments, the specific activity may range from about 100 mCi ⁶⁴Cu/µg Cu to about 500 mCi ⁶⁴Cu/µg Cu, from about 500 mCi ⁶⁴Cu/µg Cu to about 1000 mCi ⁶⁴Cu/µg Cu, from about 1000 mCi ⁶⁴Cu/µg Cu to about 1500 mCi ⁶⁴Cu/µg Cu, from about 1500 mCi ⁶⁴Cu/µg Cu to about 2500 mCi ⁶⁴Cu/µg Cu, from about 2500 mCi ⁶⁴Cu/µg Cu to about 3000 mCi ⁶⁴Cu/µg Cu, or from about 3000 mCi ⁶⁴Cu/µg Cu to about 3800 mCi ⁶⁴Cu /µg Cu. In some embodiments, the specific activity may range from about 350 ⁶⁴Cu/µg Cu to about 2300 mCi ⁶⁴Cu/µg Cu. In further embodiments, the specific activity may range from about 350 ⁶⁴Cu/µg Cu to about 500 mCi ⁶⁴Cu/µg Cu at EOB, from about 500 ⁶⁴Cu/µg Cu to about 1000 mCi ⁶⁴Cu/µg Cu at EOB, or from about 1000 ⁶⁴Cu/µg Cu to about 2300 mCi ⁶⁴Cu/µg Cu at EOB.

In general, the ⁶⁴Cu compositions disclosed herein comprise low levels of metal contaminants. The metal contaminants may be radioactive or nonradioactive. The metal contaminants may include calcium, cobalt, copper, gold, iron, lead, mercury, nickel, and zinc. For example, the 2 M HCl eluate described below in Example 5 comprises 0 ppm Au, 0 ppm Hg, < 0.02 ppm Co, < 0.2 ppm Fe, < 0.4 ppm Pb, < 0.5 ppm Ni, < 0.6 ppm Cu, and < 1.5 ppm Zn. In general, the ⁶⁴Cu compositions disclosed herein comprise less than about less than about 6 ppm total, less than about 5 ppm total, less than about 4 ppm total, or less than about 3 ppm total of cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.

The ⁶⁴Cu compositions disclosed herein may comprise a solution of hydrochloric acid (HCl) such that the solution comprises [⁶⁴Cu]CuCl₂. The solution of HCl may comprise from about 0.005 M to about 3.0 M of HCl. In some embodiments, the solution of HCl may comprise HCl at a molarity from about 0.01 M to about 2.0 M, from about 0.02 M to about 1.0 M, or from 0.04 M to about 0.06 M. In specific embodiments, the ⁶⁴Cu compositions may comprise a solution of about 0.05 M HCl.

In some embodiments, the compositions disclosed herein may further comprise at least one bifunctional chelating agent such that the copper may complex with the bifunctional chelating agent. The bifunctional chelating agent may be a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound. Examples of suitable bifunctional chelating agents include 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA), 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), 1,4,8,11-tetraazacyclotetradecane-N, N′, N″, N‴-tetraacetic acid (TETA), 5-(8-methyl-3,6,10,13,16,19-hexaaza-bicyclo[6.6.6]icosan-1-ylamino)-5-oxopentanoic acid (MeCOSar), 5-((8-amino-3,6,10,13,16,19-hexaazabicyclo(6.6.6)eicos-1-yl)amino)-5-oxopentanoic acid (sar-CO2H), di- and trimethylthiazolyl 1,4,7-triazacyclononane (TACN), diethylenetriaminepentaacetic acid (DTPA), 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA), analogs, or derivatives thereof. In specific embodiments, the bifunctional chelating agent may be DOTA. The bifunctional chelating agent may be linked to a cell targeting agent such as a peptide, protein, antibody, or fragment thereof.

(II) Processes for Producing Copper-64 - Purification by Ion Exchange Chromatography

Also provided herein are processes for preparing ⁶⁴Cu from ⁶⁴Ni, wherein the ⁶⁴Cu has high specific activity, high chemical purity, and high radionuclidic purity. ⁶⁴Cu is formed when a ⁶⁴Ni nucleus captures a proton and then emits a neutron as shown in the following reaction, ⁶⁴Ni + p → ⁶⁴Cu + n. Proton-induced production of ⁶⁴Cu occurs in a cyclotron. The processes disclosed herein are “non-carrier added” in that no inactive material or carrier is intentionally added during the production process.

The processes disclosed herein are able to produce ⁶⁴Cu in high yield and with high specific activity in one cyclotron run. Stated another way, high yield and high specific activity compositions comprising ⁶⁴Cu are obtainable from a single cyclotron target during one cyclotron run. Depending upon the various parameters, yields as high as about 40 Ci of ⁶⁴Cu may be achieved using the processes disclosed herein.

The production process comprises bombarding a ⁶⁴Ni target with a proton beam such that ⁶⁴Cu is produced, and cobalt-61 (⁶¹Co) is produced as a byproduct. The next step of the process comprises stripping the metals from the bombarded target with a strong acid (e.g., 6 M to about 12.1 M HCl) to form a strip solution. The last step of the production process comprises purifying the ⁶⁴Cu by ion exchange chromatography. The ion exchange chromatography process comprises (i) passing the strip solution through a column comprising an ion exchange resin such that ⁶⁴Cu binds to the ion exchange resin and ⁶⁴Ni passes through the column as a flow-through, (ii) rinsing the column with a volume of HCl having a molarity of about 3 M to about 6 M and (iii) adding a volume of HCl having a molarity of about 0.5 M to about 3 M to the column to elute the ⁶⁴Cu from the ion exchange resin and collecting an eluate comprising ⁶⁴Cu. FIG. 1 presents a schematic of an iteration of the process.

(A) Bombarding the Target

The proton-induced production of ⁶⁴Cu via a ⁶⁴Ni target occurs in a cyclotron. Suitable cyclotrons include low-energy cyclotrons (e.g., 3-20 MeV energy range) and medium-energy cyclotrons (e.g., 15-30 MeV range). The targets of said cyclotrons may be curved or flat. As detailed in Example 3 below, the present disclosure reveals that cyclotron targets may be bombarded at high currents with approximately 12 MeV to 13 MeV protons.

The cyclotron target may comprise a copper base layer that has been electroplated with gold to a thickness of about 50 µm. The gold-plated cyclotron target then may be plated with enriched ⁶⁴Ni. The ⁶⁴Ni may be enriched to about 98%, about 99%, about 99.6%, or about 99.9% ⁶⁴Ni. The targeting mass of enriched ⁶⁴Ni may range from about 40 mg to about 60 mg, from about 45 mg to about 55 mg, from about 48 mg to about 52 mg, or about 50 mg. The plating area may range from about 3.0 cm² to about 5.0 cm², from about 3.2 cm² to about 4.8 cm², from about 3.6 cm² to about 4.4 cm², from about 3.8 cm² to about 4.2 cm², or 4.0 cm². The plated layer of ⁶⁴Ni may have a thickness from about 8 µm to about 20 µm, from about 10 µm to about 18 µm, from about 12 µm to about 16 µm, or about 14 µm.

In the processes disclosed herein, the ⁶⁴Ni target area is bombarded with low energy protons to produce ⁶⁴Cu. In general, the proton beam of the cyclotron is adjusted to have an energy of less than about 20 MeV on the target. In some embodiments, the energy of the proton beam at the target can range from about 5 MeV to about 20 MeV, from about 7 MeV to about 17 MeV, from about 10 MeV to about 15 MeV, from about 11 MeV to about 14 MeV, from about 10 MeV to about 14 MeV, from about 11 MeV to about 12 MeV, or from about 12 MeV to about 13 MeV. In specific embodiments, the actual beam energy at the target is about 12 MeV.

The current of the proton beam may range up to about 250 µA. In some embodiments, the current of the proton beam may range from about 10 µA to about 30 µA, about 30 µA to about 100 µA, from about 100 µA to about 175 µA, or from about 175 µA to about 250 µA. In specific embodiments, the current of the proton beam may range from about 190 µA to about 230 µA, or from about 200 µA to about 225 µA.

The proton beam hits the target area at an angle. In some embodiments, the angle of the proton beam may range from about 1° to about 20°, from about 2° to about 10°, from 2° to about 8°, from about 3° to about 6°, or about 4°. In other embodiments, the angle of the proton beam may be tangential to the target area.

In some embodiments, the target radius of the proton beam may range from about 24 cm to about 32 cm, from about 26 cm to about 30 cm, from about 27 cm to about 29 cm, or about 28 cm. In certain embodiments, the target radius of the proton beam may be about 27.9 cm. In some embodiments, the proton beam may strike about 20-25%, about 15-30%, or about 10-35% of the entire target face. In other embodiments, the total area covered by the beam may range from about 1 cm² to about 16 cm², from about 2 cm² to about 8 cm², from about 3 cm² to about 6 cm², or from about 3.5 cm² to about 4.5 cm². In still other embodiments, the total area covered by the beam may be about 3.0 cm², about 3.5 cm², about 4.0 cm², about 4.5 cm², about 5.0 cm², or about 6.0 cm².

The time of bombardment may range from about 0.5 h to about 24 h. In some embodiments, the time of bombardment may range from 0.5 h to about 8 h, from about 8 h to about 16 h, or from about 16 h to about 24 h. In other embodiments, the bombardments time may range from 1 h to about 8 h, from about 2 h to about 8 h, from about 4 h to about 8 h, from about 5 h to about 8 h, or about from 5 h to about 7 h. In certain embodiments, the bombardment time may range from about 1 h to about 6 h, from about 2 h to about 6 h, from about 3 h to about 6 h, from about 4 h to about 6 h, or from about be about 5 h to about 6 h. In other embodiments, the time of bombardment may be less than 8 h, less than 7.5 h, less than 7 h, less than 6.5 h, less than 6 h, less than 5.5 h, less than 5.0 h, less than 4.5 h, or less than 4 h. In further embodiments, the time of bombardment may be about 1 h, about 2 h, about 3 h, about 4 h, about 5 h, about 6 h, about 7 h, or about 8 h. In specific embodiments, the time of bombardment may range from about 2 h to about 4 h or the time of bombardment may be about 6 h.

In specific embodiments, a cyclotron target comprising 50 mg ⁶⁴Ni is bombarded with a proton beam having an energy of about 12 MeV and a beam current of 200 µA or 225 µA for about 1 h, 2 h, 3 h, 4 h, or 6 h.

The bombarded target may comprise from about 2 Ci to about 15 Ci of ⁶⁴Cu at the end of bombardment (EOB). The bombarded target also comprises unreacted ⁶⁴Ni and ⁶¹Co that is also produced during the bombardment process. In various embodiments, the bombarded target may comprise from about 2 Ci to about 3 Ci, from about 3 Ci to about 4 Ci, from about 4 Ci to about 5 Ci, from about 5 Ci to about 6 Ci, from about 6 Ci to about 7 Ci, from about 7 Ci to about 8 Ci, from about 8 Ci to about 9 Ci of ⁶⁴Cu, from about 9 Ci to about 10 Ci, from about 10 Ci to about 11 Ci, from about 11 Ci to about 12 Ci, from about 12 to about 13 Ci, from about 13 to about 14 Ci, or from about 14 to about 15 Ci of ⁶⁴Cu. In general, longer bombardment times will yield higher levels of ⁶⁴Cu. For example, bombardment times of about 2 h to about 4 h may yield about 2 Ci to about 5 Ci of ⁶⁴Cu at EOB, bombardments times of about 6 h may yield about 5 Ci to about 9 Ci of ⁶⁴Cu at EOB, and bombardment times of about 12 h may yield about 7 Ci to about 15 Ci of ⁶⁴Cu at EOB. In general, the processes disclosed herein may produce from about 1 Ci/h to about 1.5 Ci/h of bombardment with proton beam having an energy of about 12 MeV and a current up to about 225 µA.

(B) Stripping the Bombarded Target

The next step of the process comprises stripping the ⁶⁴Ni, ⁶⁴Cu, ⁶¹Co, and other metals from the bombarded target. The metals are stripped from the target with a strong acid having a pKa of less than 1. Suitable strong acids include hydrochloric acid, nitric acid, hydrobromic acid, and sulfuric acid. In some embodiments, the bombarded target is stripped with HCl having a molarity from about 6 M to about 12.1 M (concentrated HCl). For example, the bombarded target may be stripped with about 6 M HCl, about 7 M HCl, about 8 M HCl, about 9 M HCl, about 10 M HCl, about 11 M HCl, or about 12.1 M HCl. In specific embodiments, the bombarded target is stripped with about 9 M HCl.

The stripping may comprise adding a volume of the strong acid to a chamber or holding vessel comprising the bombarded target, wherein the target is heated to a temperature from about 65° C. to about 100° C. In particular embodiments, the stripping is conducted at a temperature of about 75° C. After about 3-5 minutes, the acid may be removed and saved as the first strip solution. The target may be contacted with the strong acid several more times, and the resultant solutions combined with the first strip solution. The chamber holding the target then may be rinsed with the strong acid, and the rinse may be combined with the strip solutions to from the final strip solution. In particular embodiments, the bombarded target may be exposed three times with about 3 mL of strong acid (e.g., 9 M HCl) to generate a strip solution of approximately 9 mL.

In some embodiments, the strip solution may be evaporated to dryness or a small volume and the residue may be reconstituted in HCl of the desired molarity (e.g., 9 M) for column chromatography.

In specific embodiments, the stripping comprises contacting the bombarded target with several aliquots of 9 M HCl, at a temperature of about 65° C. to about 100° C., and collecting the aliquots as the strip solution. The chamber holding the bombarded target may be rinsed with 9 M HCl, and the rinse combined with the strip solution.

(C) Purifying ⁶⁴Cu by Ion Exchange Chromatography

The process further comprises isolating the ⁶⁴Cu from the other metals in the strip solution by ion exchange chromatography. In general, the ion exchange chromatography utilizes a strong anion exchange resin. Strong anion exchange resins generally comprise quaternary ammonium groups. For example, a strong anion exchange resin may comprise trialkyl ammonium chloride (e.g., trialkylbenzyl ammonium or trimethylbenzyl ammonium) surface groups or dialkyl 2-hydroxyethyl ammonium chloride (e.g., dimethyl-2-hydroxyethylbenzyl ammonium) surface groups. Examples of suitable strong anion exchange resins comprising trimethylbenzyl ammonium groups include AG® 1-X8 (available from Bio-Rad) and Dowex® 1X8 resin. In specific embodiments, the strong anion exchange resin may be AG® 1-X8, 100-200 mesh, chloride form.

A variety of columns sizes and bed volumes may be used to purify ⁶⁴Cu from the other metals in the strip solution. This process was developed to effectively isolate ⁶⁴Cu generated from about 50 mg of ⁶⁴Ni target material, using about 4.5 g of strong anion exchange resin in a column having an inner diameter of about 1 cm. It is understood that the amount of strong anion exchange resin may range from about 4.0 g to about 5.0 g and the inner diameter of the column may range from about 0.7 cm to about 1.25 cm without departing from the scope of the disclosure. Similarly, the volumes of the eluents passed through the column may vary depending upon the size and volume of the column and/or the amount of ⁶⁴Ni target material. In general, the ion exchange column is equilibrated with HCl (e.g., 9 M HCl) prior to the chromatography process.

(i) Removing ⁶⁴Ni

The ion exchange separation process comprises passing the strip solution to the prepared ion exchange column, as well as an additional 1 mL of 9 M HCl used to rinse the holding vessel. The strip solution may be added in multiple smaller aliquots (e.g., 3 × 3 mL, 2 × 4.5 mL, etc.) or the strip solution may be added all at once. The Ni in the strip solution does not bind to the strong anion exchange resin and passes through the column, while Cu and Co and other metals bind to the strong anion exchange resin. The column flow through may be collected as a Ni recovery fraction. The column may be rinsed with an additional volume of HCl having the same molarity as that of the strip solution to completely remove any residual Ni from the column. For example, the column may be rinsed with about 10 mL of 9 M HCl. The 10 mL may be added in multiple smaller aliquots (e.g., 5 × 2 mL, 3 × 3.333 mL, etc.) or the 10 mL may be added all at once. The column flow through from the rinse may be collected and combined with the original Ni recovery fraction. The combined Ni recovery fraction may be further processed to recover the ⁶⁴Ni, which then may be recycled and used for plating additional cyclotron targets. Nickel recovery processes are well known in the art. On average, about 82% of the target ⁶⁴Ni present in the strip solution may be recovered from the Ni recovery fraction. In various embodiments, the percentage of ⁶⁴Ni recovered in the recovery fraction may range from about 40% to about 99% of the starting ⁶⁴Ni.

(ii) Removing ⁶¹CO

The ion exchange purification process further comprises adding a volume of HCl having a molarity from about 3 M to about 6 M to the ion exchange column to elute ⁶¹Co. In various embodiments, a volume of 3 M HCl, 4 M HCl, 5 M HCl, or 6 M HCl may be added to the ion exchange column. In specific embodiments, a volume of 4 M HCl may be added to the ion exchange column. For example, about 10 mL of 4 M HCl may be added to the column. The eluent may be added in smaller aliquots (e.g., 5 × 2 mL, 3 × 3.33 mL, etc.) or as a bolus. The column eluate may be collected as a waste fraction that mainly comprises ⁶¹Co.

(iii) Isolating ⁶⁴Cu

The purification process further comprises adding a volume of HCl having a molarity from about 0.5 M to about 3 M to the ion exchange column to elute the ⁶⁴Cu. In certain embodiments, a volume of 0.5 HCl, 1 M HCl, 2 M HCl, or 3 M HCl may be added to the ion exchange column. In specific embodiments, the ⁶⁴Cu may be eluted from the ion exchange column with a volume of 2 M HCl. For example, about 8 mL to about 20 mL of 2 M HCl may be added to the column. The eluent may be added in smaller aliquots (e.g., 4 × 2 mL, 4 × 5 mL, etc.) or as a bolus. The eluate comprising ⁶⁴Cu is collected as the product of the process. On average, about 80% of the ⁶⁴Cu present in the strip solution may be recovered in the eluate comprising ⁶⁴Cu. In various embodiments, the percentage of ⁶⁴Cu recovered in the eluate comprising ⁶⁴Cu may range from about 60% to about 100%. The ⁶⁴Cu in the eluate exists as [⁶⁴Cu]CuCl₂.

The final eluate comprising ⁶⁴Cu may be evaporated to dryness (or to a smaller volume) and the resultant residue may be reconstituted in a volume of HCl having a molarity about 0.001 M to about 1 M. In various embodiments, the residue may be reconstituted in HCl having a molarity from about 0.005 M to about 0.5 M, from about 0.010 M to about 0.2 M, from about 0.025 M to about 0.1 M, or from about 0.04 M to about 0.06 M. In specific embodiments, the residue may be reconstituted in 0.05 M HCl to form a final product comprising ⁶⁴Cu.

The ⁶⁴Cu compositions prepared by the processes disclosed herein are described above in section (I).

(iv) Exemplary Ion Exchange Chromatography Purification Process

The 9 M HCl strip solution is passed through the ion exchange column, wherein ⁶⁴Cu and ⁶¹Co bind to the resin and ⁶⁴Ni flows through the column. The column is rinsed with 9 M HCl to remove residual ⁶⁴Ni. The initial column flow through and the 9 M HCL rinse can be combined as the Ni recovery fraction. The column is rinsed with 4 M HCl to elute the ⁶¹Co, which is a waste fraction. Lastly, the ⁶⁴Cu is eluted from the column with 2 M HCl.

(III) Processes for Producing Copper-64 - Purification by Extraction Chromatography and Ion Exchange Chromatography

Another aspect of the present disclosure encompasses an additional process for purifying the ⁶⁴Cu from other metals in the strip solution by a combination of extraction chromatography and ion exchange chromatography. The process comprises (a) bombarding a cyclotron target comprising ⁶⁴Ni with a proton beam to generate a bombarded target; (b) stripping the bombarded target with a volume of HCl having a molarity of about 6 M to about 12.1 M to form a strip solution comprising ⁶⁴Ni, ⁶⁴Cu, ⁶¹Co, and other metals; and (c) purifying the ⁶⁴Cu from the strip solution by chromatography, wherein the chromatography comprises (i) passing the strip solution through a first column comprising an extraction resin connected in series to a second column comprising an ion exchange resin such that the one or more metals (e.g., cationic iron) binds to the extraction resin in the first column, the ⁶⁴Cu and ⁶¹Co bind to the ion exchange resin in the second column, and ⁶⁴Ni passes through both columns as a first flow-through fraction; (ii) rinsing the first and second columns with a volume of HCl having a molarity of about 6 M to about 12.1 M to remove residual ⁶⁴Ni as a second flow-through fraction; (iii) rinsing the second column with a volume of HCl having a molarity of about 3 M to about 6 M to elute ⁶¹Co as a first waste fraction; (iv) rinsing the second column with a volume of NaCl having a molarity of about 3 M to 6 M in HCl having a molarity of about 0.01 M to about 3 M to elute residual ⁶¹Co as a second waste fraction or rinsing the second column with an additional volume of HCl having a molarity of about 3 M to about 6 M to elute ⁶¹Co as a second waste fraction; and (v) adding a volume of HCl having a molarity of about 0.01 M to about 3 M to the second column to elute the ⁶⁴Cu as a product fraction comprising ⁶⁴Cu. FIGS. 2A, 2B, and 2C present schematics or several embodiments of the dual chromatography purification process.

(A) Bombarding the Target

Suitable cyclotrons and cyclotron targets are described above in section (II)(a). The cyclotron target may comprise a copper base layer that has been electroplated with gold to a thickness of about 50 µm. The gold-plated cyclotron target then may be plated with enriched ⁶⁴Ni. The ⁶⁴Ni may be enriched to about 98%, about 99%, about 99.6%, or about 99.9% ⁶⁴Ni. The targeting mass of enriched ⁶⁴Ni may range from about 675 mg to about 825 mg, from about 700 mg to about 800 mg, from about 720 mg to about 780 mg, or about 750 mg. The plating area may range from about 17.3 cm² to about 28.8 cm², from about 18.4 cm² to about 27.6 cm², from about 20.7 cm² to about 25.3 cm², from about 21.8 cm² to about 24.2 cm², from about 22.0 cm² to about 24.0 cm², or about 23.0 cm². The plated layer of ⁶⁴Ni may have a thickness from about 21 µm to about 53 µm, from about 26 µm to about 48 µm, from about 32 µm to about 42 µm, or about 37 µm.

In the processes disclosed herein, the ⁶⁴Ni target area is bombarded with low energy protons to produce ⁶⁴Cu. In general, the proton beam of the cyclotron is adjusted to have an energy of less than about 20 MeV on the target. In some embodiments, the energy of the proton beam at the target can range from about 5 MeV to about 20 MeV, from about 7 MeV to about 18 MeV, from about 9 MeV to about 16 MeV, from about 10 MeV to about 15 MeV, from about 11 MeV to about 14 MeV, from about 12 MeV to about 13 MeV, or from about 12 MeV to about 14 MeV. In specific embodiments, the actual beam energy at the target is about 12 MeV.

The current of the proton beam may range up to about 408 µA. In some embodiments, the current of the proton beam may range from about 100 µA to about 150 µA, from about 150 µA to about 200 µA, from about 200 µA to about 250 µA, from about 250 µA to about 300 µA, from about 300 µA to about 350 µA, or from about 350 µA to about 410 µA, from about 405 µA to about 410 µA, or about 408 µA. In specific embodiments, the current of the proton beam may range from about 325 µA to about 375 µA, or from about 350 µA to about 408 µA.

The proton beam hits the target area at an angle. In some embodiments, the angle of the proton beam may range from about 1° to about 20°, from about 2° to about 10°, from 2° to about 8°, from about 3° to about 6°, or about 5°. In other embodiments, the angle of the proton beam may be tangential to the target area.

In some embodiments, the beam strike has an elliptic shape with minor and major axes. The minor axes may range from about 25.8 mm to about 34.2 mm, from about 27.9 mm to about 32.1 mm, from about 28.8 mm to about 31.2 mm, or about 30.0 mm. The major axes may range from about 84.4 mm to about 63.6 mm, from about 79.2 mm to about 68.8 mm, from about 77.0 mm to about 71.0 mm, or about 74.0 mm. In certain embodiments, the minor and major axis of the elliptic beam strike may be about 30.0 mm and 74.0 mm, respectively. In some embodiments, the proton beam may strike about 70-80%, about 60-90%, or about 55-95% of the entire target face. In other embodiments, the total area covered by the beam may range from about 14.0 cm² to about 30.0 cm², from about 28.0 cm² to about 16.0 cm², from about 26.0 cm² to about 18.0 cm², or from about 25.0 cm² to about 20.0 cm², or 23.0 cm².

The time of bombardment may range from about 0.5 h to about 24 h. In some embodiments, the time of bombardment may range from 0.5 h to about 8 h, from about 8 h to about 20 h, or from about 20 h to about 24 h. In other embodiments, the bombardment time may range from 1 h to about 24 h, from about 2 h to about 24 h, from about 4 h to about 24 h, from about 5 h to about 24 h, or about from 5 h to about 23 h. In certain embodiments, the bombardment time may range from about 1 h to about 19 h, from about 2 h to about 19 h, from about 3 h to about 19 h, from about 4 h to about 19 h, or from about 5 h to about 19 h. In other embodiments, the time of bombardment may be less than 19 h, less than 18 h, less than 17.5 h, less than 17 h, less than 16.5 h, less than 16 h, less than 15.5 h, or less than 15 h. In further embodiments, the time of bombardment may be about 8 h, about 9 h, about 10 h, about 11 h, about 12 h, about 13 h, about 14 h, or about 15 h. In specific embodiments, the time of bombardment may range from about 1 h to about 12 h or the time of bombardment may be about 12 h.

In some embodiments, a target comprising about 750 mg ⁶⁴Ni may be bombarded with a proton beam having an energy of about 12 MeV to about 14 MeV and a beam current of about 350 µA to about 408 µA for about 10 h, 12 h, 14 h, 16 h, or 19 h. In specific embodiments, two targets each comprising about 750 mg ⁶⁴Ni may be bombarded simultaneously with a proton beam having an energy of about 12 MeV to about 14 MeV and a beam current, incident on each target, of about 350 µA to about 408 µA for about 10 h, 12 h, 14 h, or 19 h.

The bombarded target may comprise from about 58 Ci to about 80 Ci of ⁶⁴Cu at the end of bombardment (EOB). The bombarded target also comprises unreacted ⁶⁴Ni and ⁶¹Co that are produced during the bombardment process. In various embodiments, the bombarded target may comprise from about 38 Ci to about 52 Ci, from about 43 Ci to about 59 Ci, from about 48 Ci to about 66 Ci, from about 52 Ci to about 72 Ci, from about 56 Ci to about 77 Ci, or from about 58 Ci to about 80 Ci of ⁶⁴Cu. In general, longer bombardment times will yield higher levels of ⁶⁴Cu. For example, bombardment times of about 12 h to about 16 h may yield about 43 Ci to about 72 Ci of ⁶⁴Cu at EOB, and bombardments times of about 19 h may yield about 58 Ci to about 80 Ci of ⁶⁴Cu at EOB. In general, the processes disclosed herein may produce from about 3.3 Ci/h to about 3.8 Ci/h of bombardment with proton beam having an energy of about 13 MeV and a current of about 350 µA or about 408 µA.

(B) Stripping the Bombarded Target

The next step of the process comprises stripping metals from the bombarded target. The metals are stripped from the target with a strong acid having a pKa of less than 1. Suitable strong acids include hydrochloric acid, nitric acid, hydrobromic acid, and sulfuric acid. In some embodiments, the bombarded target is stripped with HCl having a molarity from about 6 M to about 12.1 M. For example, the bombarded target may be stripped with about 6 M HCl, about 7 M HCl, about 8 M HCl, about 9 M HCl, about 10 M HCl, about 11 M HCl, or about 12.1 M HCl. In specific embodiments, the bombarded target is stripped with about 9 M HCl.

The stripping may comprise adding a volume of the strong acid to a chamber or holding vessel comprising the bombarded target, wherein the target is heated to a temperature from about 65° C. to about 100° C. In particular embodiments, the stripping is conducted at a temperature of about 75° C. After about 3-5 minutes, the acid may be removed and saved as the first strip solution. The target may be contacted with the strong acid several more times, and the resultant solutions combined with the first strip solution. The chamber holding the target then may be rinsed with the strong acid, and the rinse may be combined with the strip solutions to from the final strip solution. In particular embodiments, the bombarded target and the holding chamber may be contacted several times with aliquots (e.g., 5-10 mL) of the strong acid (e.g., HCl) to generate a final strip solution of approximately 20 mL to 40 mL.

In specific embodiments, the stripping comprises contacting the bombarded target with several aliquots of 9 M HCl, at a temperature of about 65° C. to about 100° C., and collecting the aliquots as the strip solution. The chamber holding the bombarded target may be rinsed with 9 M HCl, and the rinse combined with the strip solution. The strip solution comprises ⁶⁴Ni, ⁶⁴Cu, ⁶¹Co, and can contain other metals (e.g., Fe).

(C) Purifying ⁶⁴Cu by Extraction Chromatography and Ion Exchange Chromatography

The last step of the process comprises purifying ⁶⁴Cu from the other metals in the strip solution by two chromatography columns. The process comprises passing the strip solution through two columns connected in series, the first column comprising an extraction resin and the second column comprising an ion exchange resin.

Extraction chromatography resins generally comprise macroporous polymers that hold an organic complexing compound or extractant within the pore structure of the polymer. Suitable extraction chromatography extractants include tributylphosphate (TBP), carbamoyl-methylphosphine oxide (CMPO), di-(2-ethylhexyl)-phosphoric acid (D2EHPA), and dipentyl pentylphosphonate (DP[PP]). In some embodiments, the extraction chromatography extractant may be a mixture of CMPO and TBP (e.g., TRU resin; TrisKem). In specific embodiments, the extraction chromatography extractant is TBP. An example of a suitable impregnated macroporous polymer (i.e., resin) containing TBP is TrisKem TBP resin. In specific embodiments, the extraction resin may be TBP resin, 100-150 mesh, and in the chloride form.

The ion exchange column comprises a weak anion exchange resin. Weak anion exchange resins generally comprise polystyrene or polyacrylic ester frames that contain a primary, secondary, or tertiary amino group as the functional group. Suitable weak anionic functional groups include diethyl aminoethyl (DEAE) and dimethyl aminoethyl (DMAE). Examples of suitable weak anion exchange resins comprising tertiary ammonium groups include AmberLite™ FPA53 (available from Dupont) and TrisKem TK201 resin. In specific embodiments, the weak anion exchange resin is TK201 resin, 50-100 mesh, and in the chloride form.

A variety of columns sizes and bed volumes may be used to purify ⁶⁴Cu from the other metals in the strip solution. This process was developed to effectively isolate ⁶⁴Cu generated from about 750 mg of ⁶⁴Ni target material, using two distinct columns, containing extraction and weak anion exchange resins, connected in series. The first column comprises about 300 mg of extraction resin in a column having an inner diameter of 0.5 cm. It is understood that the amount of extraction resin may range from about 270 mg to about 330 mg and the inner diameter of the column may range from about 0.4 cm to about 0.6 cm without departing from the scope of the disclosure. The second column uses about 2.7 g of weak anion exchange resin in a column having an inner diameter of about 1 cm. It is understood that the amount of weak anion exchange resin may range from about 2.4 g to about 3.0 g and the inner diameter of the column may range from about 0.7 cm to about 1.25 cm without departing from the scope of the disclosure. Similarly, the volumes of the eluents passed through the column may vary depending upon the size and volume of the column and/or the amount of ⁶⁴Ni target material. In general, the columns containing extraction resin and ion exchange resin are equilibrated with HCl (e.g., 9 M HCl) prior to the chromatography process.

(i) Removing Cationic Fe and ⁶⁴Ni

The separation process comprises adding the strip solution to the prepared extraction column connected in series to the prepared ion exchange column. In this process, the strip solution volume comprises around 20 mL to around 40 mL. The strip solution may be added in multiple smaller aliquots (e.g., 4 × 10 mL, 2 × 10 mL, etc.) or the strip solution may be added all at once. The Fe in the strip solution binds to the extractant (e.g., TBP) in the first column. The Ni in the strip solution does not bind to the chromatographic resins and freely passes through both columns, while Cu and Co and other metals bind to the ion exchange column. The columns flow through volume may be collected as a Ni recovery fraction.

The columns may be rinsed with an additional volume of HCl having the same molarity as that of the strip solution to completely remove any residual Ni from the columns. For example, the columns may be rinsed with about 8 mL to about 10 mL of 9 M HCl. For example, the columns may be rinsed with about 8 mL of 9 M HCl. The volume of HCl may be added in multiple smaller aliquots (e.g., 4 × 2 mL, 2 × 4 mL, etc.) or the volume of HCl may be added all at once. The column flow through from the 9 M HCl rinse may be collected and combined with the original Ni recovery fraction. The combined Ni recovery fraction may be further processed to recover the ⁶⁴Ni, which then may be recycled and used for plating additional cyclotron targets. Nickel recovery processes are well known in the art. On average, in tracer studies that mimicked a ⁶⁴Cu purification, about 98% of the target Ni present in a simulated strip solution may be recovered from the Ni recovery fraction. In various embodiments, the percentage of Ni recovered in the recovery fraction may range from about 40% to about 99% of the starting Ni.

(ii) Removing ⁶¹Co

The separation process further comprises adding a volume of HCl having a molarity from about 3 M to about 6 M to the second column comprising the ion exchange resin to elute ⁶¹Co (and metals other than Cu). In various embodiments, a volume of 3 M HCl, 4 M HCl, 5 M HCl, or 6 M HCl may be added to the ion exchange column. In specific embodiments, a volume (e.,g., from about 10 mL to about 20 mL) of 4 M HCl may be added to the ion exchange column. For example, about 10 mL of 4 M HCl may be added to the ion exchange column. The eluent may be added in smaller aliquots (e.g., 5 × 2 mL, 3 × 3.33 mL, etc.) or the eluent may be added all at once. The ion exchange column eluate may be collected as a first waste fraction that mainly comprises ⁶¹Co.

The ion exchange column may be rinsed with an additional volume (e.g., from about 8 mL to about 10 mL) of NaCl having a molarity of about 3 M to 6 M in HCl having a molarity of about 0.01 M to about 3 M to elute residual ⁶¹Co. In specific embodiments, a volume (e.g., 8 mL) of 5 M NaCl in 0.05 M HCl may be added to the ion exchange column. The eluent may be added in smaller aliquots (e.g., 4 × 2 mL, 2 × 4 mL, etc.) or the eluent may be added all at once. The ion exchange column eluate from the 5 M NaCl eluent containing ⁶¹Co may be collected and combined with the first waste fraction containing ⁶¹Co.

Alternatively, the ion exchange column may be rinsed with an additional volume (e.g., from about 8 mL to about 10 mL) of HCl having a molarity from about 3 M to about 6 M to elute residual ⁶¹Co. In specific embodiments, a volume (e.g., 8 mL) of 4 M HCl may be added to the ion exchange column. The eluent may be added in smaller aliquots (e.g., 4 × 2 mL, 2 × 4 mL, etc.) or the eluent mL may be added all at once. The ion exchange column eluate from the 5 M HCl eluent containing ⁶¹Co may be collected and combined with first waste fraction containing ⁶¹Co.

(iii) Isolating ⁶⁴Cu

The separation process further comprises adding a volume of HCl having a molarity from about 0.01 M to about 3 M to the ion exchange column to elute the ⁶⁴Cu. In certain embodiments, a volume of 0.05 HCl, 1 M HCl, 2 M HCl, or 3 M HCl may be added to the ion exchange column. In specific embodiments, the ⁶⁴Cu may be eluted from the ion exchange column with a volume of 0.05 M HCl. For example, about 10 mL of 0.05 M HCl may be added to the ion exchange column. The eluent may be added in smaller aliquots (e.g., 5 × 2 mL, 4 × 2.5 mL, etc.) or the eluent may be added all at once. The eluate comprising ⁶⁴Cu is collected as the product of the process. On average, in tracer studies that mimicked a ⁶⁴Cu purification, about 89% of the Cu present in a simulated strip solution may be recovered in the eluate comprising Cu. In various embodiments, the percentage of ⁶⁴Cu recovered in the eluate comprising ⁶⁴Cu may range from about 60% to about 100%. The ⁶⁴Cu in the eluate exists as [⁶⁴Cu]CuCl2.

The final eluate comprising ⁶⁴Cu may be evaporated to dryness (or to a smaller volume) and the resultant residue may be reconstituted in a volume of HCl having a molarity about 0.001 M to about 1 M. In various embodiments, the residue may be reconstituted in HCl having a molarity from about 0.005 M to about 0.5 M, from about 0.010 M to about 0.2 M, from about 0.025 M to about 0.1 M, or from about 0.04 M to about 0.06 M. In specific embodiments, the residue may be reconstituted in 0.05 M HCl to form a final product comprising ⁶⁴Cu.

The ⁶⁴Cu compositions prepared by this process are described above in section (I).

(iv) Exemplary Extraction and Ion Exchange Chromatography Purification Process

The 9 M HCl strip solution is passed through a first column comprising an extraction resin connected in series with a second column comprising a weak anion exchange resin. The Fe in the strip solution binds to the extraction resin in the first column, ⁶⁴Cu and ⁶¹Co bind to the ion exchange resin in the second column, and ⁶⁴Ni flows through both columns. The first and second columns are rinsed with 9 M HCl to remove residual ⁶⁴Ni. The initial column flow through and the 9 M HCL rinse can be combined as the Ni recovery fraction. The ion exchange column is rinsed with 4 M HCl to elute the ⁶¹Co and then with 5 M NaCl in 0.05 M HCl or additional 4 M HCl to elute residual ⁶¹Co. Lastly, the ⁶⁴Cu is eluted from the ion exchange column with 0.05 M HCl.

(IV) Specific Compositions and Methods of the Disclosure

Accordingly, the present disclosure relates in particular to the following non-limiting compositions and methods.

In a first composition, Composition 1, the present disclosure provides a composition comprising from about 2 Ci to about 15 Ci of copper-64 (⁶⁴Cu) and having a specific activity up to about 3800 mCi ⁶⁴Cu/µg Cu.

In another composition, Composition 2, the present disclosure provides a composition comprising from about 2 Ci to about 15 Ci of ⁶⁴Cu at the end of bombardment (EOB) of a single cyclotron run.

In another composition, Composition 3, the present disclosure provides a composition comprising from about 2 Ci to about 5 Ci of ⁶⁴Cu at EOB of a single cyclotron run of about 2 h or about 4 h.

In another composition, Composition 4, the present disclosure provides a composition comprising from about 5 Ci to about 9 Ci of ⁶⁴Cu at EOB of a single cyclotron run of about 6 h.

In another composition, Composition 5, the present disclosure provides a composition comprising up to about 15 Ci of ⁶⁴Cu at EOB of a single cyclotron run of about 12 h

In another composition, Composition 6, the present disclosure provides a composition, as provided in any one of Compositions 1 to 5, wherein the composition has a specific activity from about 140 mCi ⁶⁴Cu/µg Cu to about 3800 mCi ⁶⁴Cu/µg Cu.

In another composition, Composition 7, the present disclosure provides a composition, as provided in any one of Compositions 1 to 6, wherein the composition has a specific activity from about 350 mCi ⁶⁴Cu/µg Cu to about 2300 mCi ⁶⁴Cu/µg Cu.

In another composition, Composition 8, the present disclosure provides a composition, as provided in any one of Compositions 3 to 7, wherein the single cyclotron run comprises bombarding a nickel-64 target with a beam of protons having an energy of about 12 MeV to about 14 MeV.

In another composition, Composition 9, the present disclosure provides a composition, as provided in any one of Compositions 1 to 8, wherein the composition has a total content of trace metals of less than about 5 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.

In another composition, Composition 10, the present disclosure provides a composition, as provided in any one of Compositions 1 to 9, wherein the composition comprises a solution of hydrochloric acid (HCl).

In another composition, Composition 11, the present disclosure provides a composition, as provided in Composition 10, wherein the solution comprises about 0.001 M to about 3 M HCl.

In another composition, Composition 12, the present disclosure provides a composition, as provided in Compositions 10 or 11, wherein the solution comprises about 2 M HCl.

In another composition, Composition 13, the present disclosure provides a composition, as provided in any one of Compositions 10 to 12, wherein the solution comprises about 0.05 M HCl.

In another composition, Composition 14, the present disclosure provides a composition, as provided in any one of Compositions 10 to 13, wherein the the ⁶⁴Cu exists as [⁶⁴Cu]CuCl2.

In another composition, Composition 15, the present disclosure provides a composition, as provided in any one of Compositions 1 to 14, wherein the composition further comprises a chelating agent or a bifunctional chelating agent in which the ⁶⁴Cu is coordinated therein.

In another composition, Composition 16, the present disclosure provides a composition, as provided in Composition 15, wherein the chelating agent or the bifunctional chelating agent is a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound.

In another composition, Composition 17, the present disclosure provides a composition, as provided in Compositions 15 or 16, wherein the bifunctional chelating agent is DOTA.

In another composition, Composition 18, the present disclosure provides a solution comprising (i) about 2 Ci to about 15 Ci of ⁶⁴Cu that has a specific activity up to about 3800 mCi ⁶⁴Cu/µg Cu and (ii) HCl.

In another composition, Composition 19, the present disclosure provides a composition, as provided in Composition 18, wherein the specific activity of the solution is from about 350 mCi ⁶⁴Cu/µg Cu to about 2300 mCi ⁶⁴Cu/µg Cu.

In another composition, Composition 20, the present disclosure provides a composition, as provided in Compositions 18 or 19, wherein the HCl has a concentration from about 0.001 M to about 3 M.

In another composition, Composition 21, the present disclosure provides a composition, as provided in any one of Compositions 18 to 20, wherein the HCl has a concentration of about 0.5 M.

In another composition, Composition 22, the present disclosure provides a composition, as provided in any one of Compositions 18 to 21, wherein the ⁶⁴Cu exists as [⁶⁴Cu]CuCl2.

In another composition, Composition 23, the present disclosure provides a composition, as provided in any one of Compositions 18 to 22, wherein the solution has a total content of trace metals of less than about 5 ppm, the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.

In another composition, Composition 24, the present disclosure provides a composition, as provided in any one of Compositions 18 to 23, wherein the solution further comprises a chelating agent or a bifunctional chelating agent in which the ⁶⁴Cu is coordinated therein.

In another composition, Composition 25, the present disclosure provides a composition, as provided in Composition 25, wherein the chelating agent or the bifunctional chelating agent is a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound.

In another composition, Composition 26, the present disclosure provides a composition, as provided in Compositions 24 or 25, wherein the bifunctional chelating agent is DOTA.

In a first process, Process 1, the present disclosure provides a process for preparing copper-64 (⁶⁴Cu) from nickel-64 (⁶⁴Ni), the process comprising (a) bombarding a cyclotron target comprising ⁶⁴Ni with a proton beam to generate a bombarded target; (b) stripping the bombarded target with a volume of hydrochloric acid (HCl) having a molarity of about 6 M to about 12.1 M to form a strip solution comprising ⁶⁴Ni and ⁶⁴Cu; and (c) purifying the ⁶⁴Cu from the strip solution by ion exchange chromatography comprising: (i) passing the strip solution through a column comprising an ion exchange resin such that ⁶⁴Cu binds to the ion exchange resin and ⁶⁴Ni passes through the column as a flow-through; (ii) rinsing the column with a volume of HCl having a molarity of about 3 M to about 6 M; and (iii) adding a volume of HCl having a molarity of about 0.5 M to about 3 M to the column to elute the ⁶⁴Cu from the ion exchange resin and collecting an eluate comprising ⁶⁴Cu.

In another process, Process 2, the present disclosure provides a process, as provided in Process 1, wherein the cyclotron target comprises about 50 mg of ⁶⁴Ni plated in an area of about 4.0 cm².

In another process, Process 3, the present disclosure provides a process, as provided in Processes 1 or 2, wherein the proton beam has an energy of about 10 MeV to about 14 MeV and a current of about 100 µA to about 250 µA.

In another process, Process 4, the present disclosure provides a process, as provided in any one of Processes 1 to 3, wherein the proton beam has an energy of about 12 MeV and a current up to about 225 µA.

In another process, Process 5, the present disclosure provides a process, as provided in any one of Processes 1 to 4, wherein the bombarding proceeds for about 1 h to about 6 h.

In another process, Process 6, the present disclosure provides a process, as provided in any one of Processes 1 to 5, wherein after the bombarding, the bombarded target comprises from about 2 Ci to about 12 Ci of ⁶⁴Cu at the end of bombardment (EOB).

In another process, Process 7, the present disclosure provides a process, as provided in Process 6, wherein after about 2 h to about 4 h of bombarding, the bombarded target comprises from about 2 Ci to about 5 Ci of ⁶⁴Cu at EOB.

In another process, Process 8, the present disclosure provides a process, as provided in Process 6, wherein after about 6 h of bombarding, the bombarded target comprises from about 5 Ci to about 9 Ci of ⁶⁴Cu at EOB.

In another process, Process 9, the present disclosure provides a process, as provided in any one of Processes 1 to 8, wherein the stripping of the bombarded target is conducted at a temperature of about 65° C. to about 100° C.

In another process, Process 10, the present disclosure provides a process, as provided in any one of Processes 1 to 9, wherein the stripping comprises contacting the bombarded target three times with an aliquot of 9 M HCl for about 3-5 minutes each time, and collecting the aliquots as the strip solution.

In another process, Process 11, the present disclosure provides a process, as provided in any one of Processes 1 to 10, wherein the bombarded target is rinsed with an additional aliquot of 9 M HCl, which is then added to the strip solution.

In another process, Process 12, the present disclosure provides a process, as provided in any one of Processes 1 to 11, wherein the ion exchange resin is a strong anion exchange resin comprising trimethylbenzyl ammonium chloride groups.

In another process, Process 13, the present disclosure provides a process, as provided in any one of Processes 1 to 12, wherein the flow-through from passing the strip solution through the column is collected as a ⁶⁴Ni recovery fraction.

In another process, Process 14, the present disclosure provides a process, as provided in any one of Processes 1 to 13, wherein after passing the strip solution through the column, a further volume of 9 M HCl is added to the column and its flow-through is combined with the ⁶⁴Ni recovery fraction.

In another process, Process 15, the present disclosure provides a process, as provided in Process 14, wherein an average of about 82% of the target ⁶⁴Ni is recovered in the ⁶⁴Ni recovery fraction.

In another process, Process 16, the present disclosure provides a process, as provided in any one of Processes 1 to 15, wherein the rinsing comprises adding 4 M HCl to the column to elute cobalt, which is collected as a waste fraction.

In another process, Process 17, the present disclosure provides a process, as provided in any one of Processes 1 to 16, wherein the ⁶⁴Cu is eluted form the column with 2 M HCl.

In another process, Process 18, the present disclosure provides a process, as provided in any one of Processes 1 to 17, wherein an average of about 80% of the ⁶⁴Cu present in the strip solution is recovered in the eluate comprising ⁶⁴Cu.

In another process, Process 19, the present disclosure provides a process, as provided in any one of Processes 1 to 18, wherein the eluate comprising ⁶⁴Cu is evaporated to dryness and reconstituted in 0.05 M HCl, thereby forming a final product comprising ⁶⁴Cu.

In another process, Process 20, the present disclosure provides a process, as provided in Process 19, wherein the final product comprising ⁶⁴Cu comprises from about 2 Ci to about 12 Ci of ⁶⁴Cu.

In another process, Process 21, the present disclosure provides a process, as provided in Processes 19 or 20, wherein the final product comprising ⁶⁴Cu has a specific activity up to about 3800 mCi ⁶⁴Cu/µg Cu.

In another process, Process 22, the present disclosure provides a process, as provided in any one of Processes 19 to 21, wherein the final product comprising ⁶⁴Cu has a specific activity from about 350 mCi ⁶⁴Cu/µg Cu to about 2300 mCi ⁶⁴Cu/µg Cu.

In another process, Process 23, the present disclosure provides a process, as provided in any one of Processes 19 to 22, wherein the final product comprising ⁶⁴Cu has a total content of trace metals of less than about 5 ppm, the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.

In another process, Process 24, the present disclosure provides an additional process for preparing copper-64 (⁶⁴Cu) from nickel-64 (⁶⁴Ni), in which the ⁶⁴Cu is purified by a combination of extraction chromatography and ion exchange chromatography. The process comprises (a) bombarding a cyclotron target comprising ⁶⁴Ni with a proton beam to generate a bombarded target; (b) stripping the bombarded target with a volume of HCl having a molarity of about 6 M to about 12.1 M to form a strip solution comprising ⁶⁴Ni, ⁶⁴Cu, ⁶¹Co, and one or more trace metals; and (c) purifying the ⁶⁴Cu from the strip solution by chromatography, wherein the chromatography comprises (i) passing the strip solution through a first column comprising an extraction resin connected in series to a second column comprising an ion exchange resin, such that the one or more trace metals binds to the extraction resin in the first column, ⁶⁴Cu and ⁶¹Co bind to the ion exchange resin in the second column, and ⁶⁴Ni passes through both columns as a first flow-through fraction. The process further comprises (ii) rinsing the first and second columns with a volume of HCl having a molarity of about 6 M to about 12.1 M to remove residual ⁶⁴Ni as a second flow-through fraction; (iii) rinsing the second column with a volume of HCl having a molarity of about 3 M to about 6 M to elute ⁶¹Co as a first waste fraction; (iv) rinsing the second column with a volume of NaCl having a molarity of about 3 M to 6 M in HCl having a molarity of about 0.01 M to about 3 M to elute residual ⁶¹Co as a second waste fraction or rinsing the second column with an additional volume of HCl having a molarity of about 3 M to about 6 M to elute ⁶¹Co as a second waste fraction; and (v) adding a volume of HCl having a molarity of about 0.01 M to about 3 M to the second column to elute the ⁶⁴Cu as a product fraction comprising ⁶⁴Cu.

In another process, Process 25, the present disclosure provides a process, as provided in Process 24, wherein the cyclotron target at (a) comprises about 750 mg of ⁶⁴Ni plated in an area of about 23.0 cm².

In another process, Process 26, the present disclosure provides a process, as provided in Processes 24 or 25, wherein the proton beam at (a) has an energy of about 10 MeV to about 15 MeV and a current of about 350 µA to about 408 µA.

In another process, Process 27, the present disclosure provides a process, as provided in any one of Processes 24 to 26, wherein the proton beam at (a) has an energy of about 13 MeV and a current of about 350 µA to about 408 µA.

In another process, Process 28, the present disclosure provides a process, as provided in any one of Processes 24 to 27, wherein the bombardment (a) proceeds for about 12 h to about 24 h, and the bombarded target comprises from about 46 Ci to about 82 Ci of ⁶⁴Cu at the end of bombardment (EOB).

In another process, Process 29, the present disclosure provides a process, as provided in Processes 28, wherein after about 16 h to about 20 h of bombarding at (a), the bombarded target comprises from about 56 Ci to about 75 Ci of ⁶⁴Cu at EOB.

In another process, Process 30, the present disclosure provides a process, as provided in Processes 28, wherein after about 19 h of bombarding at (a), the bombarded target comprises from about 62 Ci to about 73 Ci of ⁶⁴Cu at EOB.

In another process, Process 31, the present disclosure provides a process, as provided in any one of Processes 24 to 30, wherein the stripping at (b) comprises contacting the bombarded target with 9 M HCl, and the stripping at (b) is conducted at a temperature of about 65° C. to about 100° C.

In another process, Process 32, the present disclosure provides a process, as provided in any one of Processes 24 to 31, wherein the extraction resin in the first column at (c)(i) comprises tributylphosphate as a functional group, and the ion exchange resin in the second column at (c)(i) comprises a tertiary amine as a functional group.

In another process, Process 33, the present disclosure provides a process, as provided in any one of Processes 24 to 32, wherein the rinsing at (c)(ii) comprises 9 M HCl.

In another process, Process 34, the present disclosure provides a process, as provided in any one of Processes 24 to 33, wherein the first and second flow-through fractions are combined as a ⁶⁴Ni recovery fraction.

In another process, Process 35, the present disclosure provides a process, as provided in Process 34, wherein an average of about 98% of the target ⁶⁴Ni is recovered in the ⁶⁴Ni recovery fraction.

In another process, Process 36, the present disclosure provides a process, as provided in any one of Processes 24 to 35, wherein the rinsing at (c)(iii) comprises 4 M HCl, and the rising at (c)(iv) comprises 5 M NaCl in 0.05 M HCl or additional 4 M HCl.

In another process, Process 37, the present disclosure provides a process, as provided in any one of Processes 24 to 36, wherein the ⁶⁴Cu is eluted at (c)(v) with 0.05 M HCl.

In another process, Process 38, the present disclosure provides a process, as provided in any one of Processes 24 to 37, wherein an average of about 89% of the ⁶⁴Cu present in the strip solution is recovered in the product fraction comprising ⁶⁴Cu.

In another process, Process 39, the present disclosure provides a process, as provided in any one of Processes 24 to 38, wherein the product fraction comprising ⁶⁴Cu comprises from about 2 Ci to about 15 Ci of ⁶⁴Cu and has a specific activity up to about 3800 mCi ⁶⁴Cu/µg Cu.

In another process, Process 40, the present disclosure provides a process, as provided in any one of Processes 24 to 39, wherein the product fraction comprising ⁶⁴Cu has a total content of trace metals of less than about 5 ppm, the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.

DEFINITIONS

The features, structures, steps, or characteristics disclosed herein in connection with one embodiment may be combined in any suitable manner in one or more alternative embodiments.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

The terms “about” and “substantially” preceding a numerical value mean ± 10% of the recited numerical value.

Where a range of values is provided, each value between the upper and lower ends of the range are specifically contemplated and described herein.

The term “carrier,” as used herein refers to an inactive material deliberately added to a specified radioactive substance to ensure that the radioactivity will behave normally in all subsequent chemical and physical processes.

The term “non-carrier added” refers to a preparation of a radioactive isotope which is ‘free’ from stable isotopes of the element in question. More precisely, a preparation of a radioactive isotope of high specific activity to which no isotopic carrier was intentionally added and which was not produced by irradiation of a stable isotope of the same element.

EXAMPLES

The following examples illustrate various non-limiting embodiments of the present disclosure.

Example 1: Separation of Metals via Ion Exchange Chromatography

According to the literature, a bombarded Ni target typically is dissolved in 6 M hydrochloric acid (HCl) and the resulting solution is purified via anion exchange chromatography. After the nickel has completely eluted from the column, the eluent is changed to low molarity HCl (often ≤ 0.5 M) or water and the copper is collected as it is released from column. However, ⁶⁴Cu prepared this way typically contains some ⁶¹Co, as Co elutes from the resin in ≤ 4 M HCl. Thus, to obtain better separation of Co and Cu, a trial separation of various metals was performed using solutions of 6 M, 4 M, and 2 M HCl to elute Ni, Co, and Cu, respectively.

A solution containing 5.0 mg/mL Ni and 25 µg/mL each of Co, Cu, Fe, Zn, Hg and Pb in 6 M HCl was prepared to mimic an un-purified mixture. A glass Econo-column (0.7 cm x 20 cm) was dry-packed with 4.5 g of AG 1-X8 resin (16 cm bed height, 6 mL bed volume). The resin was pre-treated by washing the column with 30 mL of Chelex-treated H₂O followed by 30 mL of 6 M HCl. This rinse cycle was repeated once more so that the final wash was with 6 M HCl. The columns were gravity drained and each wash was considered complete once droplet formation ceased.

The column was loaded with 10 mL of the metal solution (50 mg Ni, 250 µg each added metal) and the flow through was collected as 2 × 5 mL fractions (load fraction). The column was eluted with the following: 5 × 2 mL aliquots of 6 M HCl (6 M fraction), 5 × 2 mL aliquots of 4 M HCl (4 M fraction), 5 × 2 mL aliquots of 2 M HCl (2 M fraction), and 1 × 5 mL aliquot of 0.5 M HCl (0.5 M fraction). Each eluate and an aliquot of the initial unpurified mixture were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Table 1 presents the amount of metal present in each fraction as a percentage of what was present in the initial unpurified mixture.

TABLE 1 Percent of metal in each fraction Load 6 M 4 M 2 M 0.5 M Ni 89.5 31.9 0.0 0.0 0.0 Co 36.5 46.5 16.7 0.0 0.0 Cu 0.0 0.0 9.6 80.6 0.1 Fe 0.0 0.0 0.0 10.7 40.7 Hg 0.0 0.0 0.0 0.0 0.0 Pb 0.4 7.2 44.0 20.0 6.4 Zn 36.9 13.1 0.0 0.0 0.0

As expected, Ni was present in the load fraction and the 6 M HCl fraction. The majority of Cu was present in 2 M HCl fraction, with a small amount (9.6%) present in the 4 M HCl fraction. Co was observed in the load, 6 M HCl, and 4 M HCl fractions, with no co-elution with Cu in the 2 M HCl fraction. Thus, there was good separation of Ni and Co from Cu, with 80.6% of the total Cu collected in the 2 M HCl faction with no co-elution of either Ni or Co. The only other tested metals present in the 2 M HCl fraction were small percentages of Pb and Fe.

Example 2: Varying Molarity of Starting Acid

To determine whether early breakthrough of Co could be reduced, as well as Pb breakthrough in the 2 M HCl fraction, the molarity of the starting acid was increased to 9 M HCl.

A solution containing 5.0 mg/mL Ni and 25 µg/mL each of Co, Cu, Fe, Zn, Hg and Pb in 9 M HCl was prepared. A column comprising 4.5 g of AG 1-X8 resin was prepared described above in Example 1. The column resin was pre-treated with 30 mL of Chelex-treated H₂O followed by 30 mL of 9 M HCl. This rinse cycle was repeated once more so that the final wash was with 9 M HCl. The prepped column was loaded with 10 mL of the Ni solution (50 mg Ni, 250 µg each added metal) and collected as 2 × 5 mL fractions. The column then was eluted, and fractions collected with the following: 5 × 2 mL fractions of 9 M HCl, 5 × 2 mL fractions of 4 M HCl, 5 × 2 mL fractions of 2 M HCl, and 1 × 5 mL of 0.5 M HCl. Samples of the eluates and the initial unpurified mixture were analyzed via ICP-OES. These data are presented in Table 2.

TABLE 2 Percent of metal in each fraction. Load 9 M HCl 4 M HCl 2 M HCl 0.5 M HCl Ni 78.7 27.6 0 0 0 Co 3.1 0.9 94.0 0.3 0 Cu 0 0 2.1 93.0 0.1 Fe 0 0 0 9.0 41.4 Hg 0 0 0 0 0 Pb 10.6 83.2 4.7 0.1 0 Zn 36.8 12.9 0 0 0

The use of 9 M HCl as the starting acid concentration improved the overall separation process by shifting the elution profiles of Co and Pb. The majority of Co was eluted in the 4 M HCl fraction (rather than the earlier fractions), and the majority of Pb was eluted in the load and 9 M HCl fractions (rather than the 4 M HCl fraction). The 2 M HCl fraction contained mainly Cu with a low percentage of Fe and trace amounts of Co and Pb.

Example 3: Adjusting a CS-30 Cyclotron to Reduce Proton Beam Energy

Copper-64 may be produced by bombarding enriched nickel-64 with low energy protons (e.g., less than 14 MeV). At higher beam energies, the production of ⁶¹Co and stable ⁶³Cu increases and ⁶⁴Cu production decreases, therefore ⁶⁴Cu production from ⁶⁴Ni via the (p,n) reaction is best performed with 12 MeV protons.

It has been generally assumed that CS-30 cyclotrons were not suitable for ⁶⁴Cu production because they may accelerate a proton beam up to about 30 MeV. It is generally accepted that a cyclotron cannot attain a beam energy lower than half of its maximum energy. Thus, the lowest energy attainable in CS-30 cyclotrons, in theory, is about 15 MeV.

The output energy of a cyclotron is given by the equation E = (rqB)²/2m, where E is the particle energy, r is the radius at which the targets are inserted, q is the charge on the particle of interest, B is the magnetic field, and m is the mass of the particle being accelerated. Since protons are being accelerated, the mass and charge are 1.672 × 10⁻²⁷ kg, and 1.602 × 10⁻¹⁹ C, respectively. The magnetic field used in CS-30 cyclotrons is 1.847 T. FIG. 3 shows the proton energy as a function of the proton beam radius. This plot predicts a target radius of about 27.9 cm to attain a beam energy of about 12 MeV.

Thus, in order to produce the desired proton beam energy of 12 MeV, the location of the target was adjusted in the cyclotron so that the proton beam would strike the target at the smaller radius of about 27.9 cm.

Initial beam strikes with CS-30 curved targets showed that the proton beam went too far along one edge of the target, all of the way to the end, with no beam on the majority of the target face, completely missing the opposite edge. Only about 25% of the entire target face had beam on it, and half of that was on an unusable edge. With this arrangement, too much of the beam would be lost, and hence it is unsuitable. This was remedied by substituting a flat target for the curved one. Using a flat target allowed the beam to strike about one-fifth of the total target area (e.g., about one-fifth from the end of the target). The total area covered by the beam was 4 cm². The beam strike from the flat target was acceptable. Tuning parameters of the CS-30 were determined to give the best beam strike at the new radius of 27.9 cm. Thus, by using a flat target, the target radius was reduced, and the energy of the proton beam could be reduced to about 12 MeV.

Example 4: Target Bombardments of Enriched Nickel-64

A CS-30 cyclotron adjusted as described above in Example 3 was used to produce ⁶⁴Cu. For this, about 50 mg of ⁶⁴Ni (~99% isotopically enriched) was electroplated on a CS-30 cyclotron flat target comprising a copper base layer that had been electroplated with gold to a thickness of about 50 µm. The plated area was about 4.0 cm². The target was bombarded with a beam energy of about 12 MeV, a beam current of 200 µA or 225 µA, and bombardment time of 1 to 6 h. The target was stripped with 9 M HCl and the resultant solution was analyzed by HPGe gamma spectroscopy to determine ⁶⁴Cu yield at the end of bombardment (EOB). Table 3 shows results of preliminary runs.

TABLE 3 Yield of Test Runs. Run Beam Current Bombardment Time ⁶⁴Cu Activity, calibrated to EOB 1 200 µA 1 h 674.1 mCi 2 200 µA 6 h 6,102 mCi 3 225 µA 1 h 1,424 \.8 mCi 4 225 µA 6 h 6,900 \.1 mCi

Example 5: Purification of Copper-64 From a Bombarded Nickel-64 Target

Flat CS-30 cyclotron targets that had been electroplated with 50 µm of gold, were plated with enriched ⁶⁴Ni, targeting a mass of about 50 mg and a plated area of 4.0 cm². The target was bombarded for 1 to 6 h with a beam energy of about 12 MeV and beam current of approximately 200 µA or 225 µA. The bombarded target was stripped using three 3.0 mL aliquots of 9 M HCl. During this time, the target stripping cell was heated to 75° C., and each aliquot was held 3-5 minutes. After the hold time, the 3-mL aliquot was removed and placed in a holding vessel. The aliquots were collected together as one, approximately 9 mL strip solution.

The ⁶⁴Cu was isolated and purified by anion exchange chromatography essentially as described above in Example 2. For this, a glass ion-exchange column (inner diameter = 1.0 cm, length = 20 cm) was nitric acid washed, rinsed with high resistivity water, and packed with 4.5 g AG 1-X8 resin (chloride form), 100 to 200 mesh (8 cm bed height, 6 mL bed volume). The column resin was pre-treated by washing twice with Chelex-treated 18.2 MΩ.cm resistivity water followed by 9 M HCl.

The 9-mL strip solution was loaded onto a pre-treated ion-exchange column along with an additional 1 mL of 9 M HCl that was used to rinse the vessel holding the strip solution. The 10-mL load volume was eluted from the column by gravity at ~1 mL per minute as the load fraction. Gravity filtration was used for all the solutions that passed through the column. The column was then rinsed with another 10 mL of 9 M HCl and the eluate was combined with the load fraction. The combined fractions (approximately 20 mL) comprised the ⁶⁴Ni recovery fraction. After the ⁶⁴Ni recovery fraction was collected from the column, 10 mL of 4 M HCl was added to the column. The eluate comprising cobalt was collected separately as a waste fraction. After the 4 M HCl fraction was collected from the column, 8 mL of 2 M HCl was added to the column. The 2 M HCl eluate collected in a separate vial and contained the ⁶⁴Cu product. The 2 M HCl eluate was evaporated to dryness and reconstituted in 0.05 M HCl to a target radioactive concentration of approximately 1.25 Ci/mL.

Aliquots of the strip solution and the eluates were analysed by gamma spectroscopy and/or with a dose calibrator to determine ⁶⁴Cu activity, and via ICP-OES to determine metallic content. The yield of ⁶⁴Cu at EOB for 15 runs ranged from 674 mCi (1 h bombardment at 200 µA) to 8,706 mCi (6 h bombardment at 200 µA). The average yield of ⁶⁴Cu at EOB for 8 runs that had a bombardment time of 6 h and beam current of 200-225 µA was 67132.6 mCi (s.d. = 1189.1). The average recovery of ⁶⁴Cu in the 2 M HCl eluate (relative to the strip solution) for the 15 runs was about 80% (s.d. = 20%). After reconstituting the ⁶⁴Cu in 0.05 M HCl, the resulting specific activity of the [⁶⁴Cu]CuCl₂ averaged 965.8 mCi ⁶⁴Cu/µg Cu (s.d. = 658) at EOB when measured by the dose calibrator, and 1,724 \.2 mCi ⁶⁴Cu/µg Cu (s.d. = 750) at EOB when measured by the HPGe detector. The Cu content was determined via ICP-OES. Further analysis revealed no statistically significant difference between the dose calibrator and the HPGe detector. The dose calibrator method was preferred because it was more straightforward to use during manufacturing. The average recovery of ⁶⁴Ni (in the ⁶⁴Ni recovery fraction) from the 15 processed targets was about 82%.

Presented below is a detailed analysis of the purified product from three representative runs. For these runs, the target was bombarded for 6 h with a beam energy of approximately 12 MeV and beam current of 200 or 225 µA. Total activity was measured with a dose calibrator calibrated for ⁶⁴Cu. Table 4 shows the activity of ⁶⁴Cu collected after the purification process. Table 4 also shows the purification process yields as amount of ⁶⁴Cu per total activity of the strip solution (as determined by dose calibrator).

TABLE 4 Recovery of ⁶⁴Cu During Purification Batch 1 Batch 2 Batch 3 Strip Solution (mCi) 9,872.0.00 10,625 10,798 2 M HCl Eluate (mCi) 6,154.4.00 8,385 8,760 % ⁶⁴Cu recovery 62.3% 78.9% 81.1 %

Table 5 presents the levels of trace metals in the 2 M HCl eluate.

TABLE 5 Trace Metal Analysis in 2 M HCl Eluate Batch 1 Batch 2 Batch 3 Au (µg/mL) 0 0 0 Co (µg/mL) 0 0 0.047 Cu (µg/mL) 0.343 0.745 0.673 Fe (µg/mL) 0.102 0.117 0.261 Hg (µg/mL) 0 0 0 Ni (µg/mL) 0.434 0.403 0.484 Pb (µg/mL) 0.031 0.031 0.886 Zn (µg/mL) 0.114 1.899 2.448

Table 6 presents the specific activity of the ⁶⁴Cu product in the 0.05 M HCl solution.

TABLE 6 Specific Activity of ⁶⁴Cu in 0.05 M HCl Solution Batch 1 Batch 2 Batch 3 ⁶⁴Cu activity (i)mC 4,041.1.00 7,650.0.00 8,109.0.00 Cu mass (µg) 2.0 8.2 5.7 Specific Activity (mCi ⁶⁴Cu/µg Cu) 2,010.5.00 937.6 1,425.2.00

Example 6. Separation of Metals via Extraction and Ion Exchange Chromatography

A trial separation of various metals was performed using a combination of extraction chromatography and ion exchange chromatography to more effectively separate Cu from masses of Ni up to 750 mg, Co, Fe, and other transition metals.

A polyethylene (PE) column (0.7 cm x 20 cm) was vacuum-packed using 20 mL of 0.05 M HCl with 2.7 g of TK201 resin (about 5 cm to 6 cm bed height, about 1 mL to 2 mL bed volume). A PE frit was securely placed atop the packed resin bed. The packed PE column, containing TK201 resin, was rinsed with 20 mL of 0.05 M HCl under vacuum. The packed PE column was capped and stored at 4.4° C.

The pre-packed PE column containing 2.7 g of TK201 resin, stored in 0.05 M HCl at 4.4° C., and a 2 mL PE column containing 300 mg of TBP resin were pre-treated by washing each column with 10 mL of high-resistivity water (HRW) followed by 10 mL of 9 M HCl. The HRW and 9 M HCl were passed through each column at a flow-rate of 1 mL/min using a syringe pump. Each wash was considered complete once droplet formation ceased.

A solution containing 25.0 mg/mL Ni, 20.4 µg/mL Co, 8.6 µg/mL Cu, 8.1 µg/mL Fe, and 10.3 µg/mL Pb was prepared in 9 M HCl to simulate a bombarded target stripping solution.

The PE columns, connected in series, were loaded at a flow-rate of 1 mL/min using a syringe pump with 30 mL of the metal solution (746 mg Ni, 259 µg Cu, 611 µg Co, 244 µg Fe, 309 µg Pb) and the flow through was collected as a single 30 mL fraction (load fraction). The two columns were eluted with 2 × 4 mL aliquots of 9 M HCl (9 M fraction) and the flow through was collected. The ion exchange column was then eluted with the following: 2 × 5 mL aliquots of 4 M HCl (4 M fraction), 2 × 4 mL aliquots of 5 M NaCl in 0.05 M HCl (5 M NaCl fraction), and 2 × 5 mL aliquot of 0.05 M HCl (0.05 M fraction). Each eluate and an aliquot of the initial mixture were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Table 7 presents the amount of metal present in each fraction as a percentage of the starting amount in the simulated stripping solution mixture.

TABLE 7 Percentages of Various Metals in Each Fraction Element Load 9 M HCl 4 M HCl 5 M NaCl 0.05 M HCl Co 53.5 7.0 21.6 11.4 n.d.* Cu n.d. n.d. n.d. n.d. 86.5 Ni 88.3 10.1 0.03 n.d. n.d. Fe n.d. n.d. n.d. n.d. n.d. Pb 75.4 11.4 0 0 0 *n.d. = not detected or below the limits of detection

As expected, Ni was present in the load fraction and the 9 M HCl rinse fraction (98.4%). The Cu was measured only in the 0.05 M HCl fraction (86.5%). Co was observed in the load, 9 M HCl, 4 M HCl, and 5 M NaCl fractions, with no co-elution of Cu in the 0.05 M HCl fraction. Thus, there was good separation of Ni and Co from Cu, with 86.5% of the total Cu collected in the 0.05 M HCl faction with no co-elution of either Ni or Co. 

What is claimed is:
 1. A composition for use as a radioactive precursor comprising from 2 Ci to 5 Ci of copper-64 (⁶⁴Cu), wherein the composition comprises chemical and radionuclidic purities suitable for positron emission tomography (PET).
 2. The composition of claim 1, wherein the composition has a total content of trace metals of less than about 6 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 3. The composition of claim 1, wherein the composition has a total content of trace metals of less than about 5 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 4. The composition of claim 1, wherein the composition has a total content of trace metals of less than about 3 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 5. The composition of claim 1, wherein the composition has a total content of trace metals of 0 ppm Au, 0 ppm Hg, <0.02 ppm Co, <0.2 ppm Fe, <0.4 ppm Pb, <0.5 ppm Ni, <0.6 ppm Cu, and <1.5 ppm Zn.
 6. The composition of claim 1, wherein the composition comprises a solution of hydrochloric acid (HCl) having a molarity of about 0.001 M to about 3 M.
 7. The composition of claim 1, wherein the ⁶⁴Cu exists as [⁶⁴Cu]CuCl₂.
 8. The composition of claim 7, wherein the composition further comprises a chelating agent or a bifunctional chelating agent in which the ⁶⁴Cu is “coordinated therein, and the chelating agent or the bifunctional chelating agent is a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound.
 9. The composition of claim 8, wherein the bifunctional chelating agent is DOTA.
 10. The composition of claim 9, wherein the radionuclidic purity of the ⁶⁴Cu is greater than 98.5%.
 11. A composition for use as a radioactive precursor comprising from 5 Ci to 9 Ci of copper-64 (⁶⁴Cu).
 12. The composition of claim 11, wherein the composition has a total content of trace metals of less than about 6 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 13. The composition of claim 11, wherein the composition has a total content of trace metals of less than about 5 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 14. The composition of claim 11, wherein the composition has a total content of trace metals of less than about 3 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 15. The composition of claim 11, wherein the composition has a total content of trace metals of 0 ppm Au, 0 ppm Hg, <0.02 ppm Co, <0.2 ppm Fe, <0.4 ppm Pb, <0.5 ppm Ni, <0.6 ppm Cu, and <1.5 ppm Zn.
 16. The composition of claim 11, wherein the composition comprises a solution of hydrochloric acid (HCl) having a molarity of about 0.001 M to about 3 M.
 17. The composition of claim 11, wherein the ⁶⁴Cu exists as [⁶⁴Cu]CuCl₂.
 18. The composition of claim 17, wherein the composition further comprises a chelating agent or a bifunctional chelating agent in which the ⁶⁴Cu is coordinated therein, and the chelating agent or the bifunctional chelating agent is a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound.
 19. The composition of claim 18, wherein the bifunctional chelating agent is DOTA.
 20. The composition of claim 19, wherein the radionuclidic purity of the ⁶⁴Cu is greater than 98.5%.
 21. A composition for use as a radioactive precursor comprising from 9 Ci to 15 Ci of copper-64 (⁶⁴Cu).
 22. The composition of claim 21, wherein the composition has a total content of trace metals of less than about 6 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 23. The composition of claim 21, wherein the composition has a total content of trace metals of less than about 5 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 24. The composition of claim 21, wherein the composition has a total content of trace metals of less than about 3 parts per million (ppm), the trace metals being cobalt, copper, gold, iron, lead, mercury, nickel, and zinc.
 25. The composition of claim 21, wherein the composition has a total content of trace metals of 0 ppm Au, 0 ppm Hg, <0.02 ppm Co, <0.2 ppm Fe, <0.4 ppm Pb, <0.5 ppm Ni, <0.6 ppm Cu, and <1.5 ppm Zn.
 26. The composition of claim 21, wherein the composition comprises a solution of hydrochloric acid (HCl) having a molarity of about 0.001 M to about 3 M.
 27. The composition of claim 21, wherein the ⁶⁴Cu exists as [⁶⁴Cu]CuCl₂.
 28. The composition of claim 27, wherein the composition further comprises a chelating agent or a bifunctional chelating agent in which the ⁶⁴Cu is coordinated therein, and the chelating agent or the bifunctional chelating agent is a macrocyclic compound, a bridged macrocyclic compound, a bicyclic compound, or an acyclic compound.
 29. The composition of claim 28, wherein the bifunctional chelating agent is DOTA.
 30. The composition of claim 29, wherein the radionuclidic purity of the ⁶⁴Cu is greater than 98.5%. 